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autoconf-2.57: unclear documentation of include files in AC_CHECK_HEADER
From: |
Nelson H. F. Beebe |
Subject: |
autoconf-2.57: unclear documentation of include files in AC_CHECK_HEADER et al |
Date: |
Fri, 7 Mar 2003 12:26:10 -0700 (MST) |
The autoconf-2.57 documentation of include files in AC_CHECK_HEADER
and others has text like this:
- Macro: AC_CHECK_HEADER (HEADER-FILE, [ACTION-IF-FOUND],
[ACTION-IF-NOT-FOUND], [INCLUDES = `default-includes'])
...
- Macro: AC_CHECK_DECL (SYMBOL, [ACTION-IF-FOUND],
[ACTION-IF-NOT-FOUND], [INCLUDES = `default-includes'])
If SYMBOL (a function or a variable) is not declared in INCLUDES
and a declaration is needed, run the shell commands
...
- Macro: AC_CHECK_SIZEOF (TYPE, [UNUSED], [INCLUDES =
`default-includes'])
Define `SIZEOF_TYPE' (*note Standard Symbols::) to be the size in
bytes of TYPE. If `type' is unknown, it gets a size of 0. If no
INCLUDES are specified, the default includes are used (*note
Default Includes::). If you provide INCLUDE, be sure to include
`stdio.h' which is required for this macro to run.
I find this rather unclear.
By experiment, what is actually expected in the includes argument is
something like this:
[
#if defined(HAVE_STDDEF_H)
#include <stddef.h>
#endif
]
but there are few examples of that in the entire autoconf manual.
The commentary cited above wrongly suggests that one should write
[INCLUDES=" stdio.h stddef.h ..."]
or
[stdio.h stddef.h ...]
or ...
I think that a short section needs to be introduced that describes the
contents of includes arguments, with links to that section from each
of the places where default-includes et al are mentioned.
Frankly, I'd prefer to see a syntax that simply listed the header
files by name, like this
AC_CHECK_SIZEOF(fpos_t,,[sys/types.h stdio.h stdlib.h])
with autoconf automatically supplying the wrapping
#if defined(HAVE_xxx_H)
#include <xxx.h>
#endif
but it is likely too late to do that, unless a clean way of handling
both styles can be identified.
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- Center for Scientific Computing FAX: +1 801 581 4148 -
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